This application is based on and claims the priority under 35 U.S.C. xc2xa7119 of German Patent Application 199 01 534.1, filed on Jan. 16, 1999 the entire disclosure of which is incorporated herein by reference.
The invention relates to a securing arrangement in a housing, including holding means that fix the position and securely hold a circuit board or similar board, plate, card or panel in a housing.
It is typical in the motor vehicle manufacturing industry, that numerous electromechanical and/or electronic components, as well as circuit boards or similar supporting plates on which such components may be mounted, are arranged in housings so as to protect the several components from damage, dirt contamination, moisture, and the like. Especially in view of the shocks that will be applied to the housing and the components therein during operation of the motor vehicle, it is necessary that the various components and/or the boards arranged in the housing must be secured in a manner that is stable and resistant to such shocks.
A securing arrangement of the above described general type for securing circuit boards in a housing is disclosed in German Utility Model DE 93 21 190 U1. The conventional securing arrangement disclosed therein provides contact pins for holding the various components such as circuit boards and the like in a housing, and further provides spring clips for securing the contact pins and the components. On the one hand, the spring clips must be embodied in such a manner so that they securely grasp around and hold the contact pins and the circuit board, and on the other hand, the spring clips must ensure that they cannot be displaced from the proper positions on the respective contact pins. For these reasons, the spring clips must exert a large spring clamping force both onto the contact pin and onto the circuit board itself. Such a complicated arrangement and the required high clamping force that must be exerted by the spring clips increases the difficulty of assembling the arrangement in the housing, increases the cost of the various parts, and therefore increases the overall manufacturing cost of the arrangement.
It is also known from German Utility Model DE G 88 10 192.4, to secure a circuit board in a housing by passing a male pin through a cut-out in the circuit board and then into a cavity in a female pin, such that the circuit board is held between a protruding shoulder of the male pin and the end face of the female pin. Such an arrangement suffers the disadvantage that the position of the two pins relative to each other must be set with extreme precision. If the male pin is inserted slightly too far into the female pin, then the space between the protruding shoulder of the male pin and the end face of the female pin becomes too small to accommodate the thickness of the circuit board, and the board can easily be cracked by the application of an excessive clamping force in a direction parallel to the axis of the pins. On the other hand, if the male pin is inserted slightly not far enough into the female pin, then the space between the protruding shoulder of the male pin and the end face of the female pin becomes too large to properly constrain the circuit board therebetween, and the circuit board will not be held securely and durably in a fixed position.
In view of the above it is an object of the invention to provide a securing arrangement for securing a circuit board or the like in a housing, that may be manufactured in a cost-economical manner, and that may be assembled fully automatically with a high process reliability while also achieving high reliability of the permanent, secure holding of the board in the housing. The invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as are apparent from the present specification.
The above objects have been achieved in a securing arrangement according to the invention, comprising a housing that includes a housing wall and at least one formed housing part such as a protrusion or positioning and securing stud (also generally called a mounting stud herein), as well as at least one securing pin. The circuit board that is to be secured in the housing has a through-hole therein, which is aligned with a hollow space of the formed housing part. Throughout this specification, the term xe2x80x9ccircuit boardxe2x80x9d will be used as an example of a board that can be secured according to the invention, but such a board may be any type of supporting board, substrate, panel, card, or plate that is to be secured in a housing.
The securing pin is inserted or pushed through the through-hole of the board and into the hollow space in the formed housing part. Thereby, the securing pin directly or indirectly secures the board relative to the formed housing part in a force-locking frictional manner so that the board cannot be displaced in the housing. For example, the securing pin exerts a substantially radially outwardly directed wedging, spreading, or pressing force directly onto the board, or indirectly through the end portion of the formed housing part onto the board. More particularly, the securing arrangement may be configured according to either of two embodiments. In a first embodiment, an end of the formed housing part is arranged flush with the board, i.e. the board rests on a free end of the formed housing part, and the securing pin directly contacts and applies a wedging force to the inner surfaces of the through-hole of the board. In a second embodiment, an end portion of the formed housing part protrudes through the through-hole of the board, and the securing pin applies a wedging force to the end portion of the formed housing part so that the end portion applies a pressing force to the inner surfaces of the through-hole.
The inventive securing arrangement provides the significant advantage that the circuit board or other plate or panel can be securely, permanently, reliably, and easily positioned, held, and fixed in the housing without requiring any additional clamping elements such as screws, rivets, spring clips, clamps, or the like, and instead the entire securing is carried out by the securing pin or pins. The securing pin extends through the through-hole in the board that is to be secured, and thereby wedgingly or pressingly holds the board in a permanent and non-displaceable manner in the housing, in that the pin is pressed into the hollow space of the formed housing part to a greater or lesser extent, and thereby achieves an adjustable or controllable wedging, spreading, or pressing effect between the securing pin and the formed housing part, and directly or indirectly also with the board that is to be secured. In this manner, a reliable securing connection is achieved in a force-locking or frictional manner, with a very simple construction, using the same materials from which the housing and particularly the formed housing part is fabricated.
The invention avoids the need of a form-locking connection, for example a connection in which the board is clampingly held in a positive form-locked configuration between two clamping shoulders or the like. The inventive arrangement especially omits the use of any sort of rim, shoulder or protrusion of the securing pin that would press against the upper surface of the board so as to hold the board between such a rim or the like and a counter surface of the formed housing part or mounting stud. No clamping forces are applied to the board in a direction parallel to the axis of the securing pin and the mounting stud, but instead only substantially radial wedging forces are applied to the inner surface of the through-hole of the board to achieve the present frictional force-locking.
As a result, it is not necessary to position the securing pin with high precision to an exact position relative to the mounting stud, but instead the securing pin may simply be inserted into the stud until the required degree of wedging force is achieved. A gradual conical taper of the securing pin ensures that a relatively large range of insertion motion of the pin will provide a fine-tuning adjustment of the wedging or pressing force that is applied substantially radially outwardly onto the inner surface of the through-hole of the board. Since there is no danger that the board will be clamped too tightly or too loosely between two opposed clamping shoulders or the like, the associated dangers of cracking the board or of producing a too-loose connection are significantly reduced or eliminated.
The present secure connection can be automatically achieved during the assembly of the components in the housing. More particularly, the automatic assembly process simply involves positioning the circuit board or other board component so that its through-hole passes over an end portion of the formed housing part, or alternatively so that the circuit board lies flushly against an end surface of the formed housing part while the through-hole of the board is aligned with the axis of the hollow space of the housing part. Then, the securing pin is simply inserted and pushed through both the through-hole of the board and also the hollow space in the formed housing part, for example with a specified insertion force, to complete the securing connection. The steps can easily be carried out by automated assembly equipment.
According to a particular embodiment detail of the invention, the securing pin has a conical shape along its axial length, and the inner hollow space of the formed housing part includes at least hollow space sections along its axial length that have an inner diameter that is smaller than the outer diameter of the securing pin at the corresponding location of the pin when the securing pin is pushed into its proper secured position in the formed housing part. Thereby, a progressively tighter wedging or clamping effect can be achieved by inserting the securing pin successively further into the formed housing part, and the securing pin is reliably held in the formed housing part by the wedging interaction of the securing pin and the above mentioned hollow space sections that have a smaller inner diameter in comparison to the respective corresponding outer diameter of the securing pin. Of course, the above comparison of the diameters relates to the respective diameters of the components in an unassembled condition, because the insertion of the pin into the hollow space necessarily deforms at least the formed housing part so that the inner diameter of the hollow space corresponds with the outer diameter of the pin. With such a conical embodiment of the securing pin, a reliable and tight securing of the board in the housing can be achieved in a very simple manner by means of the resulting wedging, spreading, or pressing effect achieved by the securing pin inserted into the hollow space of the formed housing part.
Alternatively according to the invention, the securing pin may have a cylindrical configuration along its axial length. In this case, the hollow space of the formed housing part tapers or becomes narrower along its axial length so that the inner diameter of the hollow space at the free end of the formed housing part is larger than the outer diameter of the forward end of the securing pin. At least a section or portion of the hollow space tapers to a smaller inner diameter that is smaller than the outer diameter of the securing pin at the corresponding location once the securing pin is fully seated in its final secured position in the hollow space of the formed housing part. In such an embodiment, a very simple entirely cylindrical securing pin may be used.
Preferably, the panels, boards or plates that are to be secured in the housing are circuit boards or supporting boards carrying electromechanical and/or electronic components. The inventive securing arrangement serves to fix the position of the boards in the housing, and thereby securely holds the boards and the components mounted thereon within the housing.
Another detail of the invention provides that the housing further includes a cover or lid that closes the housing once the circuit board or the like has been arranged and secured therein. The housing lid includes a protruding shoulder or a protrusion that directly contacts and presses against the end surface of the free end of the securing pin protruding out of the formed housing part after the pin has been inserted into the formed housing part for securing the circuit board or the like. In this manner, the protrusion of the housing lid ensures that the securing pin cannot inadvertently be displaced out of its securing position in the formed housing part. For example, even severe shocks applied to the housing will not cause the securing pin to be released and displaced from its proper securing position. Also, the protrusion of the housing lid ensures that the securing pin has been pushed far enough into its securing position in the formed housing part, because if the securing pin protrudes too far out of the formed housing part, then the lid cannot be mounted and closed on the housing.
As a further alternative according to the invention, the securing pin may be directly formed as an integral part of the cover or lid for the housing, whereby the securing pin protrudes from the inner side of the lid that will be facing the interior of the housing once the lid closes the housing. In such an embodiment, the number of individual components to be assembled can be further reduced, and the secure clamping and holding of the circuit board in the housing is only achieved once the lid is placed and secured onto the housing so as to close the housing. In other words, before the lid is arranged to close the housing, the board is simply loosely arranged in the proper position so that the through-hole provided in the board is aligned with the hollow space of the formed housing part, and then the lid is placed on the housing. The formed housing part is located in the housing and the pin is located on the bottom or inner surface of the lid in such a corresponding manner, so that the securing pin protruding from the bottom surface of the lid necessarily passes through a corresponding through-hole of the circuit board and then into the underlying hollow space of the corresponding formed housing part when the housing lid is placed into its proper position for closing the housing. In this manner, the number of manufacturing steps necessary for assembling the several components is also reduced.
In a preferred embodiment of the invention, the securing pin has roughened sections, and/or protrusions, such as knurling, ribs, flutes, or barbs, on its outer circumferential surface. Such features provide an enhanced frictional engagement, or even an interlocking or grasping engagement between the securing pin and the formed housing part.
The securing pin and the housing are preferably made of a synthetic plastic, or of a carbon fiber reinforced composite material. Using these materials, the overall assembly and particularly the securing arrangement can be reduced in weight and cost, while achieving a good strength and protective function of the housing and good engagement between the securing pin and the formed housing part.
It is especially advantageous if the formed housing part includes radially and axially extending slots or slits passing from the hollow space through the wall of the formed housing part, at least at a section or portion along the axial length of the formed housing part. Particularly, such slits or slots should be provided at the protruding free end portion of the formed housing part. In such an embodiment, the segments of the wall of the formed housing part divided from each other by the radial slits or slots act as elastically deflectable tongues or tabs. Thus, the securing pin inserted into such a formed housing part spreads apart the elastically deflectable tongues in the slotted portion of the formed housing part. Consequently, the individual segments or tongues of the formed housing part are pressed outwardly against the inner surface of the through-hole of the circuit board into which the free end portion of the formed housing part protrudes, so that the circuit board is very securely held onto the spread-out end portion of the formed housing part by a wedging or spreading effect.
Throughout this specification, it should be understood that the inventive arrangement may comprise a single securing pin and mounting stud combination, or may comprise a plurality of the securing pins that respectively cooperate with a plurality of through-holes provided in the board and a plurality of the mounting studs provided in the housing. Each securing pin may have the same construction and function as the other pins, and each mounting stud may have the same construction and function as the other studs. The detailed description of a single component therefore applies as well to a plurality of similar components.